Semiconductor device and method for fabricating the same

ABSTRACT

A semiconductor device includes a first field effect transistor (FET) including a first gate dielectric layer and a first gate electrode. The first gate electrode includes a first lower metal layer and a first upper metal layer. The first lower metal layer includes a first underlying metal layer in contact with the first gate dielectric layer and a first bulk metal layer. A bottom of the first upper metal layer is in contact with an upper surface of the first underlying metal layer and an upper surface of the first bulk metal layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of U.S. patentapplication Ser. No. 15/063,346 filed Mar. 7, 2016, which claimspriority to U.S. Provisional Patent Application 62/272,031 filed Dec.28, 2015, the entire disclosure of each of which is incorporated hereinby reference.

TECHNICAL FIELD

The disclosure relates to a method for manufacturing a semiconductordevice, and more particularly to a structure and a manufacturing methodfor a metal gate structure.

BACKGROUND

As the semiconductor industry has progressed into nanometer technologyprocess nodes in pursuit of higher device density, higher performance,and lower costs, challenges from both fabrication and design issues haveresulted in the development of three-dimensional designs, such as a finfield effect transistor (Fin FET) and the use of a metal gate structurewith a high-k (dielectric constant) material. The metal gate structureis often manufactured by using gate replacement technologies.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIGS. 1A-12 show exemplary sequential manufacturing process of asemiconductor device according to one embodiment of the presentdisclosure. FIGS. 1B-12 are cross sectional views corresponding to lineX1-X1 of FIG. 1A.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.”

FIGS. 1A-12 show exemplary sequential manufacturing process of asemiconductor device according to one embodiment of the presentdisclosure. FIGS. 1B-12 are cross sectional views corresponding to lineX1-X1 of FIG. 1A. It is understood that additional operations can beprovided before, during, and after processes shown by FIGS. 1A-12, andsome of the operations described below can be replaced or eliminated foradditional embodiments of the method. The order of theoperations/processes may be interchangeable.

FIG. 1A shows a top view (plan view) of a structure of a semiconductordevice after dummy gate structures are formed over a substrate. In FIGS.1A and 1B, dummy gate structures 40, 41 and 42 are formed over a channellayer, for example, a part of a fin structure 20. Each of the dummy gatestructures 40, 41 and 42 corresponds to an n-channel FET, a p-channelFET and an n-type long channel FET.

The fin structure 20 is formed over a substrate 10 and extends from anisolation insulating layer 30. For explanation purpose, the dummy gatestructures 40, 41 and 42 are formed over the same fin structure 20, butin some embodiments, dummy gate structures 40, 41 and 42 are formed overdifferent fin structures, respectively. Similarly, although two finstructures 20 are illustrated in FIG. 1A, the number of fin structureper one gate structure is not limited to two, and may be one, or threeor more.

The substrate 10 is, for example, a p-type silicon substrate with animpurity concentration in a range from about 1×10¹⁵ cm⁻³ to about 1×10¹⁸cm³. In other embodiments, the substrate is an n-type silicon substratewith an impurity concentration in a range from about 1×10¹⁵ cm⁻³ toabout 1×10¹⁸ cm⁻³. Alternatively, the substrate may comprise anotherelementary semiconductor, such as germanium; a compound semiconductorincluding Group IV-IV compound semiconductors such as SiC and SiGe,Group III-V compound semiconductors such as GaAs, GaP, GaN, InP, InAs,InSb, GaAsP, AlGaN, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; orcombinations thereof. In one embodiment, the substrate is a siliconlayer of an SOI (silicon-on insulator) substrate.

The fin structures 20 may be formed by trench-etching the substrate.After forming the fin structures 20, the isolation insulating layer 30is formed over the fin structures 20. The isolation insulating layer 30includes one or more layers of insulating materials such as siliconoxide, silicon oxynitride or silicon nitride, formed by LPCVD (lowpressure chemical vapor deposition), plasma-CVD or flowable CVD. Theisolation insulating layer may be formed by one or more layers ofspin-on-glass (SOG), SiO, SiON, SiOCN and/or fluorine-doped silicateglass (FSG).

After forming the isolation insulating layer 30 over the fin structures20, a planarization operation is performed, thereby removing part of theisolation insulating layer 30. The planarization operation may include achemical mechanical polishing (CMP) and/or an etch-back process. Then,the isolation insulating layer 30 is further removed (recessed) so thatthe upper regions of the fin structures 20 are exposed.

Then, the dummy gate structures 40, 41 and 42 are formed over theexposed fin structures 20. The dummy gate structure includes a dummygate electrode layer 44 made of poly silicon and a dummy gate dielectriclayer 43. Sidewall spacers 48 including one or more layers of insulatingmaterials are also formed on sidewalls of the dummy gate electrodelayer. The sidewall spacers 48 include one or more layers of insulatingmaterial such as silicon nitride based material including SiN, SiON,SiCN and SiOCN. The film thickness of the sidewall spacers 48 at thebottom of the sidewall spacers is in a range from about 3 nm to about 15nm in some embodiments, and is in a range from about 4 nm to about 8 nmin other embodiments.

The dummy gate structures further include a mask insulating layer 46,which is used to pattern a poly silicon layer into the dummy gateelectrode layers. The thickness of the mask insulating layer 46 is in arange from about 10 nm to about 30 nm in some embodiment, and is in arange from about 15 nm to about 20 nm in other embodiments.

As shown in FIG. 2, after the dummy gate structures are formed,source/drain regions 60 are formed. In the present disclosure, a sourceand a drain are interchangeably used, and the term source/drain refersto either one of a source and a drain. In some embodiments, the finstructure 20 not covered by the dummy gate structures is recessed belowthe upper surface of the isolation insulating layer 30. Then, thesource/drain regions 60 are formed over the recessed fin structure byusing an epitaxial growth method. The source/drain regions 60 mayinclude a strain material to apply stress to the channel region.

Then, as shown in FIG. 3, a first etching stop layer (ESL) 70 and afirst interlayer insulating (ILD) layer 75 are formed over the dummygate structures and the source/drain regions. The first ESL 70 includesone or more layers of insulating material such as silicon nitride basedmaterial including SiN, SiCN and SiOCN. The thickness of the first ESL70 is in a range from about 3 nm to about 10 nm in some embodiments. Thefirst ILD layer 75 includes one or more layers of insulating materialsuch as silicon oxide based material such as silicon dioxide (SiO₂) andSiON.

After a planarization operation on the first ILD layer 75 and the ESL70, the dummy gate structures are removed, thereby making gate spaces81, 82 and 83, as shown in FIG. 4. As shown in FIG. 4, the gate sidewallspacers 48 remain in the gate spaces.

Then, as shown in FIG. 5, a gate dielectric layer 85 is formed. The gatedielectric layer 85 includes one or more layers of dielectric material,such as a high-k metal oxide. Examples of the metal oxides used forhigh-k dielectrics include oxides of Li, Be, Mg, Ca, Sr, Sc, Y, Zr, Hf,Al, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and/ormixtures thereof. In some embodiments, an interfacial layer (not shown)made of, for example, silicon oxide, is formed over the fin structure(channel region) before forming the gate dielectric layer 85.

Further, a first work function adjustment (WFA) layer 90 for a p-channelFET is formed in the gate space 82. A blanket layer of a suitableconductive material is formed over the gate spaces and the first ILDlayer 75, and a patterning operation including lithography and etchingis performed to form the first WFA layer 90 for a p-channel FET in thegate space 82 (and the surrounding area). The first WFA layer 90includes one or more layers of conductive material. Examples of thefirst WFA layer 90 for a p-channel FET include Ti, TiAlC, Al, TiAl, TaN,TaAlC, TiN, TiC and Co. In one embodiment, Ti is used. The thickness ofthe first WFA layer 90 is in a range from about 3 nm to about 10 nm insome embodiments. The first WFA layer 90 may be formed by chemical vapordeposition (CVD), physical vapor deposition (PVD) including sputtering,atomic layer deposition (ALD) or other suitable method. As shown in FIG.5, the first WFA layer 90 is conformally formed in the gate space 82.

Then, a second WFA layer 95 for n-channel FETs is formed in the gatespaces 81 and 83. A blanket layer of a suitable conductive material isformed over the gate spaces and the first WFA layer 90, and a patterningoperation including lithography and etching is performed to form thesecond WFA 95 for n-channel FETs in the gate spaces 81 and 83 (and thesurrounding area). The second WFA layer 95 includes one or more layer ofconductive material. Examples of the second WFA layer 95 for ann-channel FET include TiN, TaN, TaAlC, TiC, TaC, Co, Al, TiAl, HfTi,TiSi, TaSi or TiAlC. In one embodiment, TiN is used. The thickness ofthe second WFA layer 95 is in a range from about 3 nm to about 10 nm insome embodiments. The second WFA layer 95 may be formed by chemicalvapor deposition (CVD), physical vapor deposition (PVD) includingsputtering, atomic layer deposition (ALD) or other suitable methods. Asshown in FIG. 5, the second WFA layer 95 is conformally formed in thegate spaces 81 and 83. It is noted that the order of forming the firstWFA layer 90 and the second WFA layer 95 can be changed. The second WFAlayer 95 is made of a different material than the first WFA layer 90.

Then, as shown in FIG. 6, a first metal material 101 for a first metallayer 100 is formed over the structure of FIG. 5. The first metalmaterial includes one or more layers of metal material, such as Al, Cu,W, Ti, Ta, TiN, TiAl, TiAlC, TiAlN, TaN, NiSi, CoSi, other conductivematerials. In one embodiment, TiN is used. The first metal material isformed by CVD, PVD, ALD, electroplating or other suitable methods. Thefirst metal layer 100 is made of a different material than at least oneof the first WFA layer and the second WFA layer.

Then, as shown in FIG. 7, a planarization operation is performed,thereby removing the upper portion of the deposited first metal material101. After the planarization operation, the first metal layer 100 isformed in each of the gate spaces. The planarization operation mayinclude a chemical mechanical polishing (CMP) and/or an etch-backprocess.

After each of the gate spaces are filled with the first metal layer 100,the first metal layers 100 are recessed (etched-back) to form gaterecesses 87, 88 and 89, as shown in FIG. 8. The upper portions of thefirst metal layers 100 are etched by using dry etching and/or wetetching. The amount (depth) D1 of the recessed portion is in a rangefrom about 20 nm to about 50 nm in some embodiments, and the height H1of the remaining first metal layer from the surface of the fin structure20 is in a range from about 30 nm to about 60 nm in some embodiments.

During the recess etching, the first WFA layer 90 and the second WFAlayer 95 are also etched.

Then, as shown in FIG. 9, a second metal material 111 for a second metallayer 110 is formed over the structure of FIG. 8. The second metalmaterial includes one or more layers of metal material, such as Al, Cu,Co, W, Ti, Ta, TiN, TiAl, TiAlC, TiAlN, TaN, NiSi, CoSi, otherconductive materials. In one embodiment, W or Co is used. The secondmetal material is formed by CVD, PVD, ALD, electroplating or othersuitable methods. The second metal material 111 is made of a differentmaterial than the first metal material (and the first and second WFAlayers) and has a higher durability against a gas containing Cl and/or Fthan the first metal material 101 (and the first and second WFA layers).

A planarization operation is subsequently performed, thereby removingthe upper portion of the deposited second metal material 111. After theplanarization operation, the second metal layer 110 is formed in each ofthe gate spaces. The planarization operation may include a chemicalmechanical polishing (CMP) and/or an etch-back process.

The planarized second metal layers 110 are further recessed in the gatespaces by using an etch-back operation, as shown in FIG. 10. The amount(depth) D2 of the recessed portion is in a range from about 10 nm toabout 40 nm in some embodiments, and the thickness T1 of the remainingsecond metal layer 110 from the upper surface of the first metal layer100 is in a range from about 10 nm to about 30 nm in some embodiments.As shown in FIG. 10, a bottom of the second metal layer 110 is incontact with an upper surface of the first metal layer 100 and an uppersurface of the first and/or second WFA layers 90, 95.

Then, as shown in FIG. 11, cap insulating layers 120 are formed over thesecond metal layers 110. The cap insulating layer 120 includes one ormore layers of insulating material such as silicon nitride basedmaterial including SiN, SiCN and SiOCN.

To form the cap insulating layers 120, a blanket layer of an insulatingmaterial having a relatively large thickness is formed over structure ofFIG. 10, and a planarization operation, such as a CMP, is performed.

Then, a second ILD 130 is formed over the structure of FIG. 11, and apatterning operation is performed to form via holes. The via holes arefiled with one or more conductive materials, thereby foil ling via plugs140, 142, 144, 146 and 148, as shown in FIG. 12. As shown in FIG. 12, awidth W1 along the X direction (a second lateral direction perpendicularto the first lateral direction) of the wide gate electrode is greaterthan a width W2 along the X direction of the narrow gate electrode.Further, one or more metal wirings (not shown) are formed over the viaplugs, respectively. A dual damascene method may be used to form the viaplugs and the metal wirings.

In the above embodiment, the second metal layers are formed by using ablanket deposition, a planarization operation and an etch-backoperation. In another embodiment, the second metal layers are directlyformed over the first metal layers. For example, after the structure ofFIG. 8 is formed, a selective deposition of W or Co is used to form thesecond metal layer over the first metal layers only in the gate spaces,to obtain the structure shown in FIG. 10. For example, by using an ALDmethod, Co and W can be selectively grown on the metal layers 90, 95 and100, while Co or W are not grown on SiO₂, SiN or other dielectricmaterials.

It is understood that the device shown in FIG. 12 undergoes further CMOSprocesses to form various features such as interconnect metal layers,dielectric layers, passivation layers, etc. In the above embodiment, themanufacturing operations for a Fin FET are described. However, the abovemanufacturing process may be applied to other types of FET, such as aplanar type FET.

The various embodiments or examples described herein offer severaladvantages over the existing art. For example, in the presentdisclosure, as shown in FIG. 12, the via plugs 140, 144 and 148 are incontact with the second metal layers 110. When via holes for the viaplugs 140, 144 and 148 are formed, a dry etching using a gas containingCl and/or F is used. If the second metal layers 110, which have a higherdurability against Cl or F, are not used, the Ti or TiN layer exposed inthe bottoms of the contact holes would be damaged (e.g., causingerosion) by the Cl or F component in the etching gas. In contrast, inthe present embodiment, since the second metal layers 110, which have ahigher durability against Cl or F that Ti and TiN, are used, damage tothe Ti or TiN layers can be avoided.

It will be understood that not all advantages have been necessarilydiscussed herein, no particular advantage is required for allembodiments or examples, and other embodiments or examples may offerdifferent advantages.

According to one aspect of the present disclosure, in a method ofmanufacturing a semiconductor device, a dummy gate structure is formedover a substrate. A source/drain region is formed. A first insulatinglayer is formed over the dummy gate structure and the source/drainregion. A gate space is formed by removing the dummy gate structure. Thegate space is filled with a first metal layer. A gate recess is formedby removing an upper portion of the filled first metal layer. A secondmetal layer is formed over the first metal layer in the gate recess. Asecond insulating layer is formed over the second metal layer in thegate recess.

According to another aspect of the present disclosure, in a method ofmanufacturing a semiconductor device, a first dummy gate structure and asecond dummy gate structure are formed over a substrate. Source/drainregions are formed. A first insulating layer is formed over the firstand second dummy gate structures and the source/drain regions. A firstgate space and a second gate space are formed by removing the first andsecond dummy gate structures, respectively. A first metal layer isformed in the first gate space, and a second metal layer is formed inthe first and second gate spaces. After forming the first and secondmetal layers, the first and second gate spaces are filled with a thirdmetal layer. A gate recess is formed by removing upper portions of thefirst, second and third metal layers formed in the first gate space, anda second gate recess is formed by removing upper portions of the firstand third metal layers formed in the second gate space. A first gateelectrode and a second gate electrode are formed by forming metal layersin the first and second gate recesses. Second insulating layers areformed over the fourth metal layers in the first and second gate recess.

In accordance with yet another aspect of the present disclosure, asemiconductor device includes a first field effect transistor (FET)including a first gate dielectric layer and a first gate electrode. Thefirst gate electrode includes a first lower metal layer and a firstupper metal layer. The first lower metal layer includes a firstunderlying metal layer in contact with the first gate dielectric layerand a first bulk metal layer. A bottom of the first upper metal layer isin contact with an upper surface of the first underlying metal layer andan upper surface of the first bulk metal layer.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A method of manufacturing a semiconductor device,the method comprising: forming a dummy gate structure over a substrate,the dummy gate structure including a dummy gate dielectric layer, adummy gate electrode layer and sidewall spacers; forming an etching stoplayer over the dummy gate structure; forming a first interlayerdielectric (ILD) layer over the etching stop layer; forming a gate spaceby removing the dummy gate electrode layer and the dummy gate dielectriclayer; forming a gate dielectric layer in the gate space and over upperportions of the first ILD layer, the etching stop layer and the sidewallspacers; forming one or more metal layers over the gate dielectriclayer; forming a gate recess by removing an upper portion of the one ormore metal layers; forming a second metal layer on a top of the one ormore metal layer, from which the upper portion has been removed, in thegate recess; and forming a cap insulating layer over the second metallayer in the gate recess, wherein: the cap insulating layer is incontact with the gate dielectric layer, and when the one or more metallayers are formed, the gate dielectric layer formed over upper portionsof the first ILD layer, the etching stop layer and the sidewall spacersis removed.
 2. The method of claim 1, wherein the forming the one ormore metal layers includes: forming a first metal layer over the gatedielectric layer leaving a remaining space in the gate space; andfilling the remaining space by forming a third metal layer.
 3. Themethod of claim 2, wherein a material of the second metal layer isdifferent from a material of the third metal layer.
 4. The method ofclaim 3, wherein the material of the first metal layer is TiN.
 5. Themethod of claim 3, wherein the material of the second metal layerincludes at least one of Co, W, Ti, Al, and Cu.
 6. The method of claim2, wherein the forming the one or more metal layers further includes:forming a fourth metal layer over the first metal layer before formingthe third metal layer.
 7. The method of claim 6, wherein a material ofthe fourth metal layer is TiAl or TiAlC.
 8. The method of claim 1,wherein the etching stop layer is one of SiN, SiCN and SiOCN and is incontact with a source/drain region.
 9. A method of manufacturing asemiconductor device, the method comprising: forming a first dummy gatestructure and a second dummy gate structure over a substrate, each ofthe first dummy gate structure and the second dummy gate structureincluding a dummy gate dielectric layer, a dummy gate electrode layerand sidewall spacers; forming a source/drain region; forming an etchingstop layer over the first and second dummy gate structures and thesource/drain region; forming a first interlayer dielectric (ILD) layerover the etching stop layer; forming a first gate space and a secondgate space by removing the dummy gate electrode layer and the dummy gatedielectric layer from the first and second dummy gate structures;forming a gate dielectric layer in the first and second gate spaces andover upper portions of the first ILD layer, the etching stop layer andthe sidewall spacers; forming a first metal layer on the gate dielectriclayer in the first gate space; forming a second metal layer on the gatedielectric layer in the second gate space and on the first metal layerin the first gate space; after forming the first and second metallayers, fully filling the first and second gate spaces with a thirdmetal layer; forming a first gate recess by removing upper portions ofthe first, second and third metal layers formed in the first gate space,and forming a second gate recess by removing upper portions of thesecond and third metal layers formed in the second gate space; forming afirst gate electrode and a second gate electrode by forming fourth metallayers on tops of the first, second and third metal layers, from whichthe upper portions have been removed, in the first gate recess and ontops of the second and third metal layers, from which the upper portionshave been removed, in the second gate recess; and forming cap insulatinglayers over the fourth metal layers in the first and second gate recess,wherein: the cap insulating layers are in contact with the gatedielectric layer, respectively, and when the third metal layer isformed, the gate dielectric layer formed over upper portions of thefirst ILD layer, the etching stop layer and the sidewall spacers isremoved.
 10. The method of claim 9, wherein a metal material of thefirst metal layer is different from metal materials of the second metallayer and the fourth metal layer.
 11. The method of claim 10, wherein:the first metal layer is TiN, the second metal layer is TiAl or TiAlC,the third metal layer is TiN, and the fourth metal layer includes atleast one of Co, W, Ti, Al, and Cu.
 12. The method of claim 9, wherein:in the first gate electrode, a bottom of the fourth metal layer is incontact with upper surfaces of the first, second and third metal layers,and in the second gate electrode, a bottom of the fourth metal layers isin contact with upper surfaces of the second and third metal layers. 13.The method of claim 9, wherein the forming fourth metal layers includes:forming a blanket layer of a metal material for the fourth metal layersin the first and second gate recesses and over the first ILD layer; andremoving upper portions of the metal material so that upper surfaces ofthe fourth metal layers are located below an upper surface of the firstILD layer.
 14. The method of claim 9, wherein the forming the fourthmetal layers includes forming a metal material for the fourth metallayers in the first and second gate recesses so that the metal materialpartially fills the first and second gate recesses.
 15. The method ofclaim 9, wherein the etching stop layer is one of SiN, SiCN and SiOCNand is in contact with the source/drain region.
 16. A method ofmanufacturing a semiconductor device, the method comprising: forming afirst dummy gate structure and a second dummy gate structure over asubstrate, the first dummy gate structure and second dummy gatestructure extending in a first lateral direction, each of the first andsecond dummy gate structures including a dummy gate dielectric layer, adummy gate electrode layer and sidewall spacers, a width along a secondlateral direction perpendicular to the first lateral direction of thesecond dummy gate structure is greater than a width along the secondlateral direction of the first dummy gate structure; forming asource/drain region; forming an etching stop layer over the first andsecond dummy gate structures and the source/drain region; forming afirst interlayer dielectric (ILD) layer over the etching stop layer;forming a first gate space and a second gate space by removing the dummygate electrode layer and the dummy gate dielectric layer from the firstand second dummy gate structures, respectively; forming a gatedielectric layer in the first and second gate spaces and over upperportions of the first ILD layer, the etching stop layer and the sidewallspacers; forming a first metal layer on the gate dielectric layer in thefirst gate space; forming a second metal layer on the gate dielectriclayer in the second gate space and on the first metal layer in the firstgate space; after forming the first and second metal layers, fullyfilling the first and second gate spaces with a third metal layer;forming a first gate recess by removing upper portions of the first,second and third metal layers formed in the first gate space, andforming a second gate recess by removing upper portions of the secondand third metal layers formed in the second gate space; forming a firstgate electrode and a second gate electrode by forming fourth metallayers on tops of the first, second and third metal layers, from whichthe upper portions have been removed, in the first gate recess and ontops of the second and third metal layers, from which the upper portionshave been removed, in the second gate recess; and forming cap insulatinglayers over the fourth metal layers in the first and second gate recess,wherein: the cap insulating layers are in contact with the gatedielectric layer, respectively, and when the third metal layer isformed, the gate dielectric layer formed over upper portions of thefirst ILD layer, the etching stop layer and the sidewall spacers isremoved.
 17. The method of claim 16, wherein: the first metal layer isTiN, the second metal layer is TiAl or TiAlC, the third metal layer isTiN, and the fourth metal layer includes Co.
 18. The method of claim 16,wherein: in the first gate electrode, a bottom of the fourth metal layeris in contact with upper surfaces of the first, second and third metallayers, and in the second gate electrode, a bottom of the fourth metallayers is in contact with upper surfaces of the second and third metallayers.
 19. The method of claim 16, wherein the etching stop layer isone of SiN, SiCN and SiOCN and is in contact with the source/drainregion.
 20. The method of claim 16, wherein the etching stop layer andone of the sidewall spacers are disposed between the first ILD layer andthe first gate electrode.